The present invention relates to a semiconductor integrated circuit for dual-band transmission/reception, in which a low noise amplifier is integrated, in a mobile terminal set for dual-band wireless communications, mainly applied to a wireless communication system for operating in two frequency bands, including a high frequency band and a low frequency band.
FIG. 4 shows an example of the construction of a terminal device to which a conventional semiconductor integrated circuit for dual-band transmission/reception (hereinbelow referred to as a xe2x80x9ctransmission/reception ICxe2x80x9d) is applied. This is applied to a mobile terminal of a wireless communication system for operating in two different frequency bands. A transmission/reception IC 401 has a receiving mixer 403a for the high frequency band and a receiving mixer 403b for the low frequency band, applied to the dual-band wireless communication system, a next-stage mixer 404, a variable gain amplifier 405, a demodulator 406, a modulator 408, an offset PLL 409, and a divider 407. A local oscillation signal necessary for frequency conversion is supplied from a synthesizer 410 and external RF-VCO (Voltage Controlled Oscillator) for the high frequency band 413a, RF-VCO for the low frequency band 413b, internal IF-VCO 412 and the internal divider 407. A band pass filter 411 connected to the transmission/reception IC removes out-band spurs. An amplifier 402a for the high frequency band and an amplifier 402b for the low frequency band are external devices of the IC. In the transmission part, VCO for the high frequency band 414a and VCO for the low frequency band 414b are external. The local oscillation signal from the VCO is inputted to offset PLL 409 and the frequency of the modulated signal is converted to the transmission frequency. The high power amplifier for the high frequency band 415a and the high power amplifier for the low frequency band 415b amplify the transmission signal and the band pass filter 416 removes out-band spurs. So far, it has been difficult to IC-incorporate the low noise amplifier due to shortage of gain in the high frequency band and noise characteristic by fT limitation of the transistor operation and the capacitance of the transistor substrate. However, the above problems have been overcome by recent improvements in fine processing, and so a low noise amplifier can be incorporated.
An example of a low noise amplifier applied to a dual-band transmission/reception IC is disclosed in xe2x80x9cDual-band High-Linearity Variable-Gain Low-Noise Amplifiers for Wireless Applicationsxe2x80x9d by Keng Leong Fong, ISSCC 1999, pp. 224-225, p. 463. This construction, in which two low noise amplifiers for the dual-band transmission/reception IC are integrated as one chip and are sealed in a TSSOP20 pin package, does not include the entire transmission/reception system. Note that correspondence between the signal lines, the ground line and the like and the pads is unknown. Further, an example of a transmission/reception IC including a low noise amplifier is disclosed in xe2x80x9cA Single-Chip CMOS Transceiver for DCS1800 Wireless Communicationsxe2x80x9d by Michiel Steyaert et al., ISSCC 1998, pp. 48-49, p. 411. This construction, in which a transmission/reception circuit is integrated as one chip, is not applied to dual-band communications. Correspondence between the signal lines, the ground line and the like and the pads is unknown. Further, the package used there is unknown.
In the present invention, the low noise amplifiers 402a and 402b are newly provided in the transmission/reception circuit chip 401 for the dual-band communications, as shown in FIG. 4. In this case, problems in pin layout in the package have been found. Note that in the present invention, a Quad Flat package (hereinbelow abbreviated to xe2x80x9cQFPxe2x80x9d) where pins are provided along four sides is employed as the package.
As a first problem, in a layout where the low noise amplifier is bonded to a long lead pin among lead pins of the QFP with a long bonding wire, the amount of feed-back by parasitic inductance is large, and the high frequency gain and noise characteristic are degraded.
As a second problem, high-frequency characteristics of the IC are similarly degraded due to transformer coupling between IC pins and transformer coupling by wiring intersection on a multilayer substrate on which the IC is packaged.
As a third problem, oscillation may occur due to parasitic capacitance and parasitic inductance in the low noise amplifier.
It is an object of the present invention to provide a pin layout which prevents degradation of high frequency characteristics of the low noise amplifier included in the IC for dual transmission/reception.